The invention relates generally to semiconductor devices and more particularly to unguarded Schottky barrier diodes.
A diode is an electrical component that allows current to flow in one direction, but not in the other. FIG. 1 is a circuit symbol of a typical Schottky barrier diode 100, where the diode 100 has an anode 102 (metal) in direct contact with a cathode 104 (n-type doped semiconductor material). In Schottky barrier diodes, conventional current can typically flow from the anode 102 to the cathode 104, but not from the cathode to the anode. Schottky barrier diodes typically result in fast switching times and low forward voltage drop, relative to conventional p-n diodes.
Schottky barrier diodes are available in guarded and unguarded diode configurations. Guarded Schottky barrier diodes include a p-n junction guard ring disposed in the substrate around the perimeter of the diode. Although the p-n junction guard ring eliminates some adverse leakage current effects around the perimeter, at higher forward bias (especially for high barrier height silicides) there is significant injection of minority carriers. This injection leads to very slow diode recovery after the forward bias is removed. This phenomenon cannot be tolerated in many high speed applications.
Therefore, many high speed applications require integrated unguarded Schottky barrier diodes to be able to operate at high reverse bias voltages while offering very fast recovery speeds. For some time, however, these diodes have suffered from hot carrier damage even after a modest reverse bias of 10-15 volts or less. This hot carrier damage can lead to unguarded Schottky barrier diodes with non-ideal I-V characteristics. Accordingly, there is a need for improved unguarded Schottky barrier diodes and manufacturing techniques.